How to change UIScrollView contentSize after UITextField resigns first responder - iphone

Question

I'm writing an iPhone app and I have some UITextfields that will get covered when the keyboard appears; therefore I put the UITextFields in a UIScrollView, and set myself as the delegate so that when the the keyboard becomes active, this method gets called:
-(void) textFieldDidBeginEditing:(UITextField *)textField
{
self.myScrollView.contentSize = CGSizeMake(self.myScrollView.contentSize.width, 560);
[self.myScrollView setContentOffset:CGPointMake(0, 200) animated:YES];
}
Note, that I am making the contentSize taller so that even once the textfields have been brought into focus, the user can still scroll.
Similarly, when the textfield resigns first responder status, this method gets called:
-(void) textFieldDidEndEditing:(UITextField *)textField
{
[self.myScrollView setContentOffset:CGPointMake(0, 0) animated:YES];
self.myScrollView.contentSize = CGSizeMake(self.myScrollView.contentSize.width,self.myScrollView.frame.size.height);
}
Note, that once the keyboard has been lowered, all the content is visible, thus there is no need for scrolling to be enabled (contentSize = frame.size).
However, my problem is because I am setting the contentSize right after the contentOffset is set, the setContentOffset animation does not have time to be completed. Instead, the animation looks extremely jerky. Any suggestions?

Answer 1

Working with UIKeyboardDidShowNotification and UIKeyboardWillHideNotification is a good idea:
Step 1: listen to the two notification
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardDidShow:)
name:UIKeyboardDidShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWillBeHidden:)
name:UIKeyboardWillHideNotification object:nil];
Step 2: do something while the keyboard did show
- (void)keyboardDidShow:(NSNotification*)notification
{
CGSize keyboardSize = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size;
BOOL Need_Resize; // judge by yourself
if (Need_Resize) {
double offset; // judge by yourself
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDelegate:self];
[UIView setAnimationDuration:0.5];
[UIView setAnimationBeginsFromCurrentState:YES];
[self.view setCenter:CGPointMake(self.view.center.x, self.view.center.y - offset];
[UIView commitAnimations];
}
}
Step 3: do something while the keyboard did hide
// in animation code, set the view back to the original place
[self.view setCenter:CGPointMake(self.view.center.x, self.view.frame.size.height/2)];
This solution does not need UIScrollView, just adjust the view's place, with animation, it looks great enough.

Answer 2

What about this?
Don't know if it will work but just from the top of my head:
[UIView animateWithDuration:0.5
animations:^{
self.myScrollView.contentSize = CGSizeMake(self.myScrollView.contentSize.width, 560);
} completion:^(BOOL finished) {
[self.myScrollView setContentOffset:CGPointMake(0, 200) animated:YES];
}];
Good luck

Answer 3

Instead of setting the content offset you could try using scrollRectToVisible:animated: and pass it the rect of your textfield or CGRectZero depending on which direction you're going.